1. Field of The Invention
The invention relates to a cutting tool and, more particularly, to a cutting tool having one or more replaceable cutting inserts which can be clamped to the toolholder and which feature, on the supporting and/or clamping surfaces, elements for achieving a formfitting, correctly located positioning.
2. Description of the Related Art
In cutting tools having replaceable cutting inserts, the cutting inserts are fixed to the toolholder using a wide variety of clamping elements. One widely used clamping method consists of providing the cutting inserts with a central hole, which are fixed to the toolholder by means of screws with appropriate head shapes or with clamping elements that engage directly on the wall of the central hole, such as eccentrics or tilting pins. Other known clamping elements are, for instance, clamping claws that engage the cover surface of the indexable, replaceable insert, causing the cutting insert to be attached to the toolholder.
In the case of cutting inserts for cutoff or parting, which as a rule are extended in length, it is customary to improve clamping by providing the cutting inserts with a concave or convex V-shaped supporting and/or clamping surface and to subject the clamping surface to the necessary clamping force via a threadable clamping claw or by means of elastic segments of the toolholder and/or the seating blade through the elastic deformation of these segments.
Inasmuch as on modern machine tools the cutoff inserts are often used not only for parting or recessing, but also for producing surface contouring by turning or facing, it is unavoidable that such cutting inserts are also stressed by lateral compressive or tensile forces. For such cutting operations, the clamping force exerted upon the cutting insert is often insufficient so that, despite these V-shaped supporting and/or clamping surfaces, there may result a shifting or even a pullout of the cutting insert from the toolholder. This results in dimensional deviation of the work piece in process, reduced working life because of premature wear, breakage or loss of the cutting insert, as well as damage to the tool bit seat or the clamping parts on the toolholder.
Such deficiencies involving an occasionally inadequate attachment of the cutting insert to the toolholder led to the introduction-over and above the customary clamping elements--of mutually coordinated elevations and recesses in the contact surfaces between the cutting insert and the toolholder. This was done to provide an additional positive form fit between the cutting insert and the toolholder and thus leads to improved positioning possibilities and to an improved clamping of the cutting inserts in the toolholder. Examples of such designs of cutting inserts and toolholders are described in DE-OS 36 17 119, DE-OS 26 53 222 and DE-GM 92 01 113.
A disadvantage of such known tool bit attachments is the fact that the production of such additional formfitting registering elements is expensive; they must be provided both on the tool bits and on the toolholders and must be precisely adjusted to one another, in order to ensure that the tolerances required for the cutting tool with respect to the position of the cutting edge are maintained.